Short pulse-high energy electron radiation tube



March 9, 1965 w. P. DYKE ETAL 3,

SHORT PULSE-HIGH ENERGY ELECTRON RADIATION TUBE Filed 001- 22, 1962 2Sheets-Sheet 1 I/VVE/VTORS WALTER P. DYKE FRANK J. GRUNDHAUSER 5')BUCKHORN, BLORE, KLAROUIST a SPARKMAN ATTORNEYS March 9, 1965 w. P. DYKEETAL 3,173,006

SHORT PULSE-HIGH ENERGY ELECTRON RADIATION TUBE Filed Oct. 22, 1962 2Sheets-Sheet 2 Fig. 4

Fig. 6

Fig. 7 Fig. 8

IN V EN TORS.

WALTER P. DYK E BY FRANK J GRUNDHAUSER BUCKHORN, BLORE, KLARQUIST 8SPARKMAN ATTORNEYS United States Patent C) 3,173,006 SHORT PULSE HIGHENERGY ELECTRON RADIATIGN TUBE Walter P. Dyke and Frank J. Grundhauser,McMinnviile,

Greg, assignors to Field Emission Corporation, Mc-

Minnviile, Greg, a corporation of Oregon Filed Oct. '22, 1962, 591'. No.232,021

12 Claims. (Cl. 250-495) This invention relates to an electron radiationdevice and more particularly to a device by which various substances canbe subjected to intense pulses of electron radiation.

It is frequently desirable to determine the biological, chemical orphysical ellect of radiation such as electron radiation upon varioussubstances, such as living organisrns or electronic components.Important factors are the intensity of the radiation or dose rate aswell as the time during which the radiation is applied to the substanceunder test. Previous radiation sources have been limited to relativelong pulse lengths of radiation and relative low dose rates. For examplesuch pulse lengths have, in general, been greater than one microsecondand dose rates substantially less than rads per second.

In accordance with the present invention practical electron radiationtubes have been developed in which electrons are emitted from a cathodestructure at least partly by field emission and are caused to pass athigh velocity through a thin walled anode structure and penetrate asubstance being treated in a manner which can produce much greater doserates and shorter pulse lengths of radiation. Thus measured dose ratesas high as 2 10 rads per second have been produced with pulse lengths ofthe order of 0.03 to 0.1 microsecond. In one embodiment of the inventionthe substance to be subjected to electron radiation is introduced intothe interior of a hollow anode structure having a thin metal Wall andelectrons traveling at high velocity from a cathode structure at leastpartly surrounding the anode structure are caused to penetrate the wallfrom a plurality of directions in paths which con verge toward suchsubstance. The anode and cathode structures are both supported within anevacuated envelope but access to the interior of the anode structurefrom the exterior of the envelope is provided so that substance to betreated can be introduced and removed from the anode structure. I

The anode structure may be of circular cylindrical shape having itscylindrical wall of thin metal and having one end closed by a metallicend member. The other end may be secured to the end of a metal tubeextending through the wall of the envelope to provide both an electricalconnection to the anode structure and access to the intetier of theradiation chamber provided by such anode structure. The cathodestructure may also be of generally circular cylindrical shape and beconcentric with and positioned to surround the anode structure. Thegeneral type of cathode structure is preferably that of the combinedfield emission and vacuum arc type employing a plurality of groups ofneedle points such as shown in the copending application of Walter P.Dyke and Frank J. Grundhauser, Serial No. 114,125, filed June 1, 1961,although it may be of the combined thermal and field emission type shownin the copending application of Walter P. Dyke and Frank J. Grundhauser,Serial No.

- 160,534, filed December 19, 1961, in which a plurality of 3,173,006Patented Mar. 9, 1965 tions in accordance with either of the twoembodiments of the invention disclosed herein, more uniform irradiationis accomplished and also larger samples can be treated. If it is desiredto subject one side only of the material to electron radiation to alimited depth, then a Single end fire tube of the type discussed abovecan be employed.

The electrode structures of either embodiment may be energized by storedenergy type of pulsers of the general type shown in the copendingapplication of Walter P. Dyke, Frank I. Grundhauser and Norman W.Stunkard, Serial No. 103,796, filed April 18, 1961. Pulsers of suchgeneral type have been developed delivering as high as 2000 amperes at 2million Volts to provide a 4 billion watts discharge for very shortperiods of time, for eX- ample, in squarewave pulses of 0.03 to 0.1microsecond. The tubes of the present invention are operable with suchpulse discharges.

It is therefore an object of the present invention to provide animproved tube structure for subjecting substances to electron radiation.

Another object of the invention is to provide improved electronradiation tubes by which substances to be treated can be subjected tohigh intensity electron radiation for very short periods of time.

Another object of the invention is to provide an electron radiationdevice by which a material can be irradiated with electron incident froma plurality of sides of the sample to thereby irradiate the sample moreuniformly than if such electrons were incident from one side only andalso to enable larger samples to be thus irradiated.

Another object of the invention is to provide a tube structure in whichsubstances to be subjected to electron radiation can be introduced intoand removed from a chamber in a thin walled anode structure through anaccess passageway open to the atmosphere and such substance can besubjected to radiation by high speed electrons penetrating the wall ofsuch chamber.

A further object of the invention is to provide an electron radiationtube in which high speed electrons are produced by a high voltage, highcurrent electric discharge in a vacuum at least in part by fieldemission from a cathode structure and caused to penetrate through thewall of a thin walled anode into a substance to be irradiatcd.

Other objects and advantages of the invention will appear in thefollowing description of a preferred embodiment shown in the attacheddrawing of which:

FIG. 1 is a longitudinal sectional view through a tube in accordancewith the present invention with the anode structure and part of thecathode structure shown in side elevation;

FIG. 2 is a fragmentary longitudinal sectional view on an enlarged scaleof the anode structure of FIG. 1;

FIG. 3 is a vertical section on an enlarged scale taken on the line 3-3of FIG. 1;

FIG. 4 is a view similar to FIG. 1, showing a modified tube;

FIG. 5 is an end elevation of the tube of FIG. 1;

FIG. 6 is a partial sectional view showing how three of the tubes ofFIGS. 1 and 2 may be supported to provide for electron radiation of amaterial from a plurality of directions;

FIG, 7 is a sectional view of the support and anode connector of FIG, 6;and

FIG. 8 is a bottom view of the support and connector ing at its innerend in a press seal 14, through which a pair of cathode leads 16 alsoprovide support elements for a cathode structure 18.

The cathode structure is shown as being in the form of a hollowopen-ended cylindrical member supported coaxially of the envelope 1t)and fabricated from four sheet metal arcuate elements 2t) and fourcathode needle supporting blocks 22. The arcuate elements arecircumferentially spaced and each extends somewhat less than 90 aroundthe cylindrical cathode structure. The axially extending edges of thearcuate elements are bent outwardly to provide flanges 24. The needlesupporting blocks are rectangular elements elongated axially of thecathode structure and are positioned between adjacent edge flanges 24 ofcontiguous arcuate elements 20. Such adjacent edge flanges extendparallel to each other and the flanges of each set of adjacent flangesare secured to the opposite sides of one of the needle support blocks inany suitable manner, such as spot welding. Corresponding edge flanges 2-2- of two diametrically opposed arcuate elements 24) are also eachsecured to one of the supporting cathode leads 16, for example, by spotwelding.

The needle supporting blocks 22 each has a plurality of spaced sharpneedle points 26 supported thereon and directed inwardly toward an anodestructure 28, also of hollow cylindrical conformation and supportedwithin and coaxial of the cathode structure 18. The needles and theirsupporting blocks can be fabricated in any of a number of ways andmethods of making and supporting such needle points are discussed in thecopending application Serial No. 114,125 referred to above. Such needlepoints may have tip curvatures with radii ranging from 10- tocentimeters and may be, for example, spaced 1 to mills apart and mayproject from their supporting blocks 22 a distance of the order of tomills.

The inner or needle supporting portions of the blocks 22 also preferablyextend inwardly from the resulting inner circular cylindrical surface ofthe cathode structure provided by the arcuate elements 20. The result isan electron emitting and electron stream focusing structure whichresults in large numbers of electrons being emitted from the needlepoints 26 by combined field emission and vacuum arc action and directedat high velocity to the anode structure 28 when a high voltage pulsefrom a source capable'ot supplying a large pulse of current is appliedbetween the cathode structure and anode Structure. Ionization of metalvapor from the needle points take place but the high voltage pulse isdiscontinued before an are causing removal of metal from the anodeelement takes place. Metal is thus removed from a few of the needlepoints on each block 22 during each operation of the tube but suificientneedle points are provided so that the tube is capable of a large numberof successive operations.

The anode structure includes a circular cylindrical hollow anode element30 of thin metal secured at one end to the open end of an anodestructure metal support tube 32 'to provide for free communicationbetween the interior of the tube 32 and the anode structure 30. Theother end of the anode element St) is closed by ametallic disc 34.- toprovide an anode chamber 36 within the anode element 30.

The anode support tube 32 extends axially of the envelope through ametal cup element 38 which has its peripheral edges sealed into theinner end of another reentrant portion at of the envelope it) at theother end of the envelope from the reentrant portion 12. Such cup membermay be made of any one of several known or suitable alloys selected tohave a thermal coeflicie'rit of expansion close to that of the glass ofthe reentrant por- .tion 40. A reinforcing collar 42 is positionedwithin the cup element 33 and around the tube 32.' Such cup is securedto the cup 38 and the tube 32 in order to rigidly support the tube andthe anode element 28 carried thereby. It will be apparent that the anodechamber 36 is sealed from the vacuum in the envelope 10 but is open tothe atmosphere through the tube 32. A container or other holder 44diagrammatically indicated in FIG. 2 and mounted upon the end of ahandle or wire 46 of suitable length and containing or having on itsouter surface any suitable substance to be subjected to electronradiation may be inserted into and withdrawn from the anode chamber 36through the tube i The cup member 38 may also have a suitable anodeconnector element tfi secured thereto and it willbe apparent thatelectrical connections to a source of high voltage, high current pulsesof electrical energy can be made through the anode connector element 4-8and the cathode leads 16. It will also be apparent that the usual getterelement (not shown) can be connected between the cathode leads 16 andenergized during evacuation of the envelope 15'.

The tube of the present invention may obviously be made in various sizesbut as a specific example, the diameter of the anode element 30 may be 1cm. and the length '2 cm. Also the wall thickness of such element may beof the order of 1 mil. Such element may be of any one of a number ofmetals, for example, beryllium, titanium or molybdenum. Each of thecathode needle supporting blocks 21?. may, for example, be of copper andbe 0.6 inch long and support a number of needle points 26 of the orderof 100, such needle points being of tungsten or other metal. forexample, be supported 1.3 cm. from the surface of the anode element 30.The electrons emitted from the needle points are directed toward theanode element in part by the arcuate elements 29 which act as focusingelements so that the beams from the groups of cathode needle pointsconverge toward and strike the anode elements.

The tube shown in FIGS 4 to 6 includes a tubular glass member 50 formingpart of the envelope of the tube and having a reentrant portion 52 atone end into which is sealed a pair of cathode leads 54 which support attheir ends within the envelope a cathode needle supporting block 56 ofthe same general type as the needle supporting blocks 22 describedabove. The needle supporting block is provided with spaced needle points26 also of the type discussed above. The needle points 26 of the tube ofFIGS. 4 to 6 are, however, directed toward the end 58 of the tubeopposite the reentrant portion 52.

The end 58 of the glass tubular member 56 is flattened into an elongatedoval and is sealed to an oval-shaped envelope closure cup 6%) of asuitable metal having a thermal coeilicient of expansion similar to thatof the glass of the end 58. The closure cap 60 has a rectangular opening62 therein in alignment with the needle points 26. The opening 62 isclosed by a window 64 of thin metal, such as one of the metals discussedabove with respect to the anode element 30 of FIGS. 1 to 3. The window64 provides an anode element and may be of the same or even lesserthickness than the anode element 39 of FIGS. 1 to 3.

A plurality of the tubes shown in FIGS. 4 and 5 may be supported withtheir anode or cap ends adjacent each other, for example, by insertingthe caps 69 of three of such tubes into oval flanged sockets 66 formedin the three sides of a sheet metal support and anode connector elementas. The sockets 66 receive and fit the caps 60. It will be apparent thatthe tubes of FIG. 6 will be operated in parallel and that suitablecathode and anode connections will be provided. The material to beirradiated by electrons will be positioned in the anode chamber 7 itprovided in the anode structure formed by the anode ends of the tubes.Such material may be supported in suitable thin walled containers or, itthe nature of the substance permits, the material may be supported onone of the envelope closures provided by a cap 6% and window 64 withoutthe use of a special container for the material. i

It is apparent that the high dosage rates of radiation Such needlepoints may, a

referred to above require high electron beam current densities, forexample, of the order of 500 amperes per square centimeter, and thateven at pulse lengths of 0.1 microsecond or shorter there isconsiderable heating of the anode element. This heating increases thedensity of the metal employed, for example, the heating due to suchelectron beams traversing a 0.001 inch molybdenum element once only,will cause the temperature of such element to rise to 400 C. For alesser density material such as beryllium, such temperature is less than100 C. The upper limiting factor for the high voltage electron beamcurrent is thus the heating which is produced when a particular metal isemployed for the anode element and the temperature which such metal willwithstand with out destruction of the anode element 28. The temperaturewhich the particular material being treated can withstand is of courseanother limiting factor.

It will also be apparent from the preceding discussion that a portion ofthe energy of the high speed electrons is lost by inelastic collisionwith atoms of the metal of the anode element during passage through suchanode element and, in fact, all of such electrons do not pass throughsuch element. For example, with molybdenum the number of electronshaving an initial energy of 600,- 000 electron volts passing through ananode element of 1 mil thickness is approximately 83 percent and theresidual energies of the electrons which do pass through range between550,000 and 570,000 electron volts. Elements having lower atomic numbersthan molybdenum transmit a greater number of electrons for the samethickness of the anode element and with less decrease in the energies ofthe transmitted electrons. The materials treated in the anode chamberare thus not subjected to a truly monoenergic beam of electrons but thisis not possible in any event, since an energy spread is produced as soonas the electrons penetrate such substance. Since the electrons reach thesubstance being treated from several directions, the uniformity oftreatment of such substance is greater than in previous systems,employing a beam of electrons from one direction only.

While we have disclosed a preferred embodiment of the invention, it isintended that the scope of the invention should not be limited to thedetails of such specific embodimerlt.

We claim:

1. An electron radiation device comprising envelope means having avacuum therein,

an anode structure forming part of said envelope means,

said anode structure having a thin metallic wall portion capable ofbeing penetrated by high speed electrons, electron emitting meanssupported in said envelope means including a field emission cathode fordirecting electrons toward said wall portion when a high voltage pulseis applied between said anode and said cathode, means for supportingmaterial to be subjected to electron radiation adjacent and on the otherside of said wall portion from said electron emitting means,

and electrical connecting means for said electron emitting means andsaid anode structure to enable high voltage, high current electricdischarges to be produced between said electron emitting means and saidanode structure to cause electrons to penetrate said wall and into saidmaterial.

2. An electron radiation device comprising envelope means having avacuum therein,

an anode structure forming part of said envelope means, said anodestructure providing a hollow chamber open to the atmosphere forreceiving material to be subject to electron radiation and having aplurality of thin wall portions located around said chamber,

a plurality of electron emitting means each including at least one fieldemission cathode and supported in said envelope means for directingelectrons toward said wall portions, when a high voltage pulse isapplied between said anode structure and the cathodes of said electronemitting means,

and electrical connecting means for said electron emitting means andsaid anode structure to enable high voltage, high current electricdischarges to be produced between said electron emitting means and saidanode structure to cause electrons to penetrate said wall portions andinto said material from a plurality of directions.

3. An electron radiation device comprising envelope means having avacuum therein,

an anode structure forming part of said envelope means, said anodestructure providing a hollow chamber open to the atmosphere :forreceiving material to be subject to electron radiation and having aplurality of thin wall portions spaced around said chamber,

a plurality of electron emitting means each including at least one fieldemission cathode supported in said envelope means -for directingelectrons toward said wall portions, when a high voltage pulse isapplied between said anode structure and said electron emitting means,

means for applying high voltage pulse between said electron emittingmeans and said anode structure to enable high voltage, high currentelectric discharges to be produced between said electron emitting meansand said anode structureto cause electrons to penetrate said wallportions and into said material from a plurality of directions,

said envelope means including a plurality of separate envelopes eachhaving one of said thin wall portions at one end thereof and eachcontaining at least one of said electron emitting means,

and said anode structure including means for supporting said pluralityof envelopes with their ends having said thin wall portions adjacenteach other.

4. An electron radiation device comprising:

envelope means having a vacuum therein,

an anode structure supported by said envelope means,

said anode structure providing a hollow chamber having its interiorsealed from said vacuum and open to the atmosphere, and having a thinmetallic wall capable of being penetrated by high speed electrons toprovide an electron radiation chamber,

a field emission cathode structure supported in said envelope means andhaving electron emitting means for directing electrons toward said wallwhen a high voltage pulse is applied between said anode and cathodestructures,

means providing access to the interior of said chamber from the exteriorof said envelope means without affecting said vacuum to enable theintroduction into and removal from said chamber of a material to besubject to electron radiation,

and means for applying high voltage pulses between said anode andcathode structure to enable high voltage, high current pulse electricdischarges to' be produced by combined field emission and vacuum arcoperation between said cathode and anode structures to cause electronsto penetrate said wall and into said material.

5. An electron radiation tube comprising:

an envelope having a vacuum therein,

an anode structure supportedin said envelope,

said anode structure including a hollow member having its interiorsealed from said vacuum to provide a chamber within said member andhaving a thin metallic Wall surrounding said chamber capable of beingpenetrated by high speed electrons,

a field emission cathode structure supported in said envelope and atleast partly surrounding said anode structure and having electronemitting means in the form of a plurality of spaced needles fordirecting psi electronstow rd said wall when a high voltage :pulse isapplied between said anode and cathode structures, I I

means providing access to the interior of said chamber from the exteriorof said envelope without atiecting said vacuum to enable theintroduction into and removal from said chamber of a material to besubject to electron radiation;

and electrical connection means extending from the exterior of saidenvelope to said anode and cathode structures to enable high voltage,high current pulse electric discharges to be produced betweensaidcathode and anode structures to cause electrons to penetrate :said walland =into said material.

'6. An electron radiation tube comprising:

an envelope having a vacuum therein,

an anode structure supported within said envelope,

said anode structure including a hollow cylindrical inernber havingits-interior sea-led from said vacuum to provide a chamber within saidmember and having a thin metallic cylindrical wall surrounding saidchamber'capable ofbeing penetrated by high speed electrons,

a plurality of field emission cathode structure supported in saidenvelope and at least partly surrounding said anode structure and havingelectron emitting means 'fo'r directing electrons-toward said wall froma pluraitt pf directions wheri azliig'li vdlt-age;pttlse is appliedbetween :said anode and cathode structures,

meanstproviding acces'szto-the interior of s'aid'chamber from theexterior of said envelope without affecting said'vacuiimito enable theintroduction into and :remov'al from said chamber ofa-ma'terialrto besubject to electron radiation,

and electrical connection meansextendingzfrom the ex- *terioriof saidenv'elope'to said anode and cathode structures to enable high voltage,ihigh'currentipulse electric dischargesvtobeiproduced between said:cathads and anode structures tocaus'eelectrons to ,pe'netrate said wallandinto said material.

7. :An electron Fradiation tube. comprising:

an envelope :having ?a vacuum therein,

an Fanode structure supported within said envelope,

said anode structure including a hollow cylindrical member 'having itsinterior sealed from said vacuum and having a thin metallic cylindrical'wall capable of being penetrated ibyhi-gh speed electrons :to .provide'an electron radiation chamber,

a cathode structure supported in said envelope and extending around:said ano'd'e-"structu're and having'electron emitting means spacedradially V-from and circumferentially around'$said member for directing:electrons by field emission toward "said wall from a plurality ofdirections :when a high voltage pulse is applied betweensaidanodeandcathodestructures,

means for introducingmaterial:intothe interior of said chamber from ftheexterior: of said -envelope :without affecting said vacuumiand :forremoving said material from said chamber to subject ititoelectronradiation,

'and'electrical connectionmeans extending from the ex- =terior'of saidZenvelope=to said :anode vand cathode structures to enable high voltage,highJcurrenttpulse electric discharges tobe produced betweensaid cathodeand anode structures to cause-electrons to penetrate said wall and into.said material.

8. An electronradiation tube comprising:

an elongated envelope having 'a vacuum' therein,

an anode structuresupported in saide'nvelope-and having its interiorsealed from-said'vacuum,

said anode structure including an "elongated hollow member extendingaxially of said: envelope 'and having a thin-metallic wall capable'ofbei'ngpenetratcd by' high speed electrons-to provide an electron radiatin Cham e a cathode structure supported in said envelope and havingelectron emitting means for directing electrons by field emission towardsaid wall when a high voltage pulse is applied between said anode andcathode structures,

means providing access into said chamber without affecting said vacuumincluding a hollow metallic tube extending axially of said envelope andopening into one end of said chamber and to the exterior of saidenvelope to enable the introduction into and :removal from said chamberof a material to be subject to electronradiation,

and electrical connection means extending from the exterior ofsaid'envelope to said anode and cathode structures to enable highvoltage, high current pulse electric discharges to be produced betweensaid cathode and anode structures to cause electrons to penetrate saidwall and into said-material.

9. An electron radiation tube comprising:

an elongated envelope having a vacuum therein,

an anode structure supported in said envelope and including a hollowcylindrical member having its interior-sealedfrom said vacuum,

said anode structure having its cylindrical axis extend- -in-g axiallyof said envelope and having a thin metallic :cylindrical wall capable ofbeing penetrated by high-speed electrons to provide anelectronrradiationchamber,

a hollow cathode structure supported in said-envelope and surroundingsaid anode-structure,

said cathode structure having electron emitting means circumfe'rentiallydisposed around said anode structure for directing electrons by fieldemission toward said wall whena high voltage pulse is applied--between-said anode-and cathode structures,

means providing access intosaid-chamber without affeoting said vacuumincluding a hollow metallic-tube extending axially of said envelope andopening into anend of said chamber and to the exterior ofsaid envelopetoenable theintroduction into and removal from said chamber of aimaterialto be subject to=elec- "tron radiation,

and electrical connection :means including said tube extending from theexterior of said envelope to said anode and cathode structures to enablehigh voltage, .high current pulse electric discharges to be producedbetween said cathode andranode structures to cause :electrons topenetrate-said-wall andintosaid material.

10. An electron radiation jtubeicomprisingz an elongated envelope havinga vacuum therein and having reentrant ends, 1

'ananode structure in said envelope and including a hollowcylindricalmember extending axially of said envelope,

saidanodestructure having its interior sealed from said vacuum andhaving a thin metallic cylindrical wall capable of being penetrated byhigh speed electrons to provide an; electronradiation chamber,

a:field'emission-cathodestructure in said envelope and surrounding saidanodestructure and having electron emitting "means disposedcircumferentially around said anodestructure for directing electronstoward said wallwhen abigh voltage pulse is applied between saidanodean'd cathode structures,

means for supportingsaid anode andproviding access into said chamberincluding a hollow metallic tube extending axially of said envelopeandopening into an end of said chamber and to :the exterior'o-t saidenvelope to enable-the introduction into :andremoval -from said chamberof a-material to be subject to electron radiation, 7

said tube being supported'by and opening'through the inner portion ofone of said reentrantends of said envelope, and electrical connectionmeans including said tube extending from the exterior of said envelopeto said anode and cathode structures to enable high voltage, highcurrent pulse electric discharges to be produced between said cathodeand anode structures to cause electrons to penetrate said wall and saidmaterial, said connection means also including leads extending throughthe inner portion of the other of said reentrant ends of said envelopeand supporting said cathode structure.

11. An electron radiation tube comprising:

an envelope having a vacuum therein,

an anode structure supported in said envelope,

said anode structure including a hollow member having its interiorsealed from said vacuum and having a thin metallic wall capable of beingpenetrated by high speed electrons to provide an electron radiationchamber,

a field emission cathode structure supported in said envelope and havingelectron emitting means for directing electrons toward said wall when ahigh voltage pulse is applied between said anode and cathode structures,

said electron emitting means including a plurality of needle pointsdirected toward said wall from a plurality of sides of said anodestructure,

means providing access to the interior of said chamber from the exteriorof said envelope without affecting said vacuum to enable theintroduction into and removal from said chamber of a material to besubject to electron radiation,

and electrical connection means extending from the exterior of saidenvelope to said anode and cathode structures to enable high voltage,high current pulse electric discharges to be produced between saidcathode and anode structures to cause electrons to penetrate said walland into said material.

12. An electron radiation tube comprising:

an envelope having a vacuum therein,

an anode structure supported in said envelope,

said anode structure including a hollow cylindrical member having itsinterior sealed from said vacuum and having a thin metallic cylindricalwall capable of being penetrated by high speed electrons to provide anelectron radiation chamber,

a cathode structure including a hollow cylindrical member supported insaid envelope and concentric with and surrounding said anode structure,

electron emitting means including a plurality of electron emittingelements supported within and spaced circumferentially of said hollowcylindrical member of said cathode structure,

said electron emitting elements each including a plurality of fieldemission cathodes in the form of spaced needle points directed towardsaid wall,

means to provide access to the interior of said chamber from theexterior of said envelope without affecting said vacuum to enable theintroduction into and removal from said chamber of a material to besubject to electron radiation,

and electrical connection means extending from the exterior of saidenvelope to said anode and cathode structures to enable high voltage,high current pulse electric discharges to be produced between saidcathode and anode structures to cause electrons to penetrate said walland said material.

Reterences Cited in the file of this patent UNITED STATES PATENTS897,279 Fressenden Sept. 1, 1908 1,385,121 Elliott July 19, 19211,970,532 Bouwers Aug. 14, 1934 2,907,704 Trump Oct. 6, 1959

1. AN ELECTRON RADIATION DEVICE COMPRISING ENVELOPE MEANS HAVING AVACUUM THEREIN, AN ANODE STRUCTURE FORMING PART OF SAID ENVELOPE MEANS,SAID ANODE STRUCTURE HAVING A THIN METALLIC WALL PORTION CAPABLE OFBEING PENETRATED BY HIGH SPEED ELECTRONS, ELECTRON EMITTING MEANSSUPPORTED IN SAID ENVELOPE MEANS INCLUDING A FIELD EMISSION CATHODE FORDIRECTING ELECTRONS TOWARD SAID WALL PORTION WHEN A HIGH VOLTAGE PULSEIS APPLIED BETWEEN SAID ANODE AND SAID CATHODE, MEANS FOR SUPPORTINGMATERIAL TO BE SUBJECTED TO ELECTRON RADIATION ADJACENT AND ON THE OTHERSIDE OF SAID WALL PORTION FROM SAID ELECTRON EMITTING MEANS, ANDELECRICAL CONNECTING MEANS FOR SAID ELECTRON EMITTING MEANS AND SAIDANODE STRUCTURE TO ENABLE HIGH VOLTAGE, HIGH CURRENT ELECTRIC DISCHARGESTO BE PRODUCED BETWEEN SAID ELECTRON EMITTING MEANS AND SAID ANODESTRUCTURE TO CAUSE ELECTRONS TO PENETRATE SAID WALL AND INTO SAIDMATERIAL.